Flattening an array

Hello,
We have the following code:
$tmpemail = mysql_query("SELECT email_address

FROM users

WHERE users.status = 'Active'", $conn) or die('Query failed: ' . mysql_error());
while ($row = mysql_fetch_array($tmpemail, MYSQL_ASSOC))

{

$recepients = $row["email_address"];

}
The above array $row["email_address"] contains a number of email addresses. We want the variable $recepients to have all the email addresses in it and with semi-colons in between, for example "abc@jjj.com; rabbit@dog.com; babyyou@waggg.com", etc ...
What can be done to flatten this array?
Thank you in advance.